In the prior art, as the recording material embedded in cards such as credit cards, bank cards, etc., magnetic recording materials have been primarily used. While such magnetic recording materials have the advantage that writing and reading of information can be easily performed, and forging of information can be effected with relative ease, there is the problem that high-density information recording cannot be achieved.
In recent years, from the standpoint of the recording and reproduction of high-density information, development of IC cards and optical cards has been progressing. Among them, optical cards using optical recording and reproduction systems have the advantage that the information density recorded is substantially higher when compared to that of the magnetic system of the prior art or that by the IC system.
In this connection, as the optical recording member or the optical recording material to be used for such an optical card, there have been proposed in the prior art those as described below.
For example, the example shown in FIG. 18A is an example of an optical recording member of the so-called ROM (read only memory) type. In this case, on the optical card 50 is formed an optical recording member constituted of a high reflectance portion 51 and a low reflectance portion 52, with the information recording bit constituted of the low reflectance portion 52. FIG. 18B is a sectional view of said optical card 50, having a light reflective material 55 corresponding to an information recording pattern formed on a transparent substrate 54 according to photolithography, while a member having a black printed layer 57 on a base material 58 is bonded through and adhesive layer 56 to form the optical card 50. Therefore, in this case, the reading of information is performed by detecting the difference in light reflectance between the light reflective material 55 and the printed layer 57.
FIG. 19 is an example of an optical recording member of the ROM type disclosed in Japanese Patent Publication No. 48357/1983, and in the case of this example, an information recording bit 62 with a light reflectance differing from the surrounding portion 61 is formed by effecting pattern exposure and development corresponding to the recording information on the film of a silver halide emulsion formed on a certain base material.
On the other hand, the example shown in FIG. 20 is an example of an optical recording member of the so-called DRAW type (direct-read-after-write type) which can "directly read after writing". In this case, one surface of the photopolymer 71 is formed in uneven shape, a thin film of an optical recording material 72 such as Te, etc., is provided along the uneven surface, which is then bonded to the substrate 74 with an adhesive 73, and at the same time on the upper surface of the polymer 71 is laminated a light-transmissive acrylic resin, etc., to constitute an optical recording member. Writing of information onto the optical recording member is effected, as shown in FIG. 21, by scanning the uneven portion of the optical recording material 72 with an irradiated laser beam 76 to confirm the position by focusing on, for example, the convex portion, and thereafter writing the bit information at the convex portion of the optical recording material 72.
To describe an optical recording member of the DRAW type of the prior art disclosed in Japanese Patent Publication No. 48357/1983 by referring to FIG. 22, in this case, a film 80 of a silver halide emulsion is formed on a base material, and pattern exposure and development are effected on the film 80, thereby forming 81 and 82 with different light reflectances. Bit information is written on the portion 81 by confirming the position of the portion 81 through the difference in light reflectance.
However, according to the best of our knowledge, the optical members of the prior art as described above are all have relatively cumbersome preparation steps, and when production and copying are performed in large amounts, they cannot necessarily be said to be economical methods. Also the optical members obtained are not yet sufficiently satisfactory with respect to long-term storability durability.
For example, in the optical recording member shown in FIG. 18 as mentioned above, since patterning of the light reflective material is effected by wet etching with a strong acid, etc., the steps of washing the etchant and drying are cumbersome and take a long time, and also if washing is insufficient, corrosion will proceed with lapse of time after completion to shorten the life of the optical recording member. Also, pH management of the etchant is generally difficult, and further there is also involved the problem that troubles may be generated due to impurities in the etchant.
Also, in the optical recording medium shown in FIG. 19, since a certain degree or higher of precision is required for the height and the width in formation of a convex surface, it has the problem that the method for controlling such precision will become necessarily difficult, and for the purpose the preparation steps will become complicated to involve the problem of increased cost.
Also, in the optical recording member shown in FIG. 22 as mentioned above, because only precision is required for the width of the track, production can be performed more easily than that of the optical recording member in FIG. 20 as mentioned above, but since a specific photographic material of a special silver halide emulsion, etc. is required, there is involved the problem that the production cost is increased.